It seems like having more people makes everything more efficient. For example, with hiking if you have 100 + people single file on a trail , the guy in front can stop, take a break, and rejoin at the end without everyone having to stop. repeat.
From an individual perspective, how is it any faster than walking alone (or everyone taking the same break at once, assuming they don't take any time to regroup or string out). If it isn't more efficient from any given person's perspective (for all of the walkers), it isn't better for the group.